PS to my former message:
Would it be possible to feed the dac 1321 simply with 7 V via the barrel connector (normally 5 V power input)?
No, you will burn things.... But if you look at the dac1321 picture on the soekris website, there is a J7 connector just after the switching supply's transformer, that could be used to supply +- 7V directly....
Seems like I would need two LPS then. You could use them centre tapped to get +/- 7 V. That would be a psu double the price of the DAC. That is a wee bit of am exaggeration I suppose. Beside the fact that combining the two psu to get +/- 7 V is beyond my skills. On the other hand the 5 V 1.1 A through the barrel connector might be a tad low, 5.5 W for max. 3 W power consumption.
If you do not use the digital volume control or if you do not listen at very low volume this should not be a problem in my opinion. 25 bits gives you lots of headroom. If the music is recorded with a mic it will not have more then 15 bit. That leaves you 10 bit or 60 dB of attenuation. Two more bits would be nice but are they necessary? The price difference is also considerable.
Hi Matt,
ifi power might be an intermediate step.
Hi TNT,
that is what dither is for. As you said this applies to most digital volume controls, whether you start out with 27 (1451 and 1421) or 25 bits (1321), that is the reason why I like my passive transformer based attenuator.
I do not need the additional imputs the 1421 has, actually USB is all I need. So 25 bits should be ok, 0.8 or 0.3 pS clock jitter not sure I would hear any difference.
Best Regards
Dithering is needed every time recalculation has been performed. Volume control is re-calcultion. If one do an operation on a 16 bit word, carried in a 16 bit deep system, the bit depth is still 16 bit after the operation but dither is still required to get rid of the errors introduced by te operation.
A 16bit signal can not have 120 dB clinical dynamic range.
From: Dynamic range - Wikipedia :
"In digital audio theory the dynamic range is limited by quantization error. The maximum achievable dynamic range for a digital audio system with Q-bit uniform quantization is calculated as the ratio of the largest sine-wave rms to rms noise is:[19]
snip...
The 16-bit compact disc has a theoretical undithered dynamic range of about 96 dB,[20][d] however, the perceived dynamic range of 16-bit audio can be 120 dB or more with noise-shaped dither, taking advantage of the frequency response of the human ear.[21][22"
NB: "can be..." the DAM don't incorporate dither so for a 16 bit signal it will be 96 dB or less if the digital volume control is engaged and set to attenuate. This is theory and can't be argued. For 24 bit signals, it's a better situation. Just to be really clear - for 16 bit audio the 25/27 bit deep processing "lanes" in the DAMs don't matter.
The SBAF test was made at 24 or maybe even 32 bit PCM wide payload (test signal)?
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IMHO:
If your input, or computational result, has more bit-resolution than your output/intermediate signal.....
Well, this isn't the case in a DAM volume control... it's the opposite.
So you mean that dither only really works in some nice numerical combinations?
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Looking at the way Soeren has powered the 1541, I cannot avoid thinking whether one could do the same with the 1021. Two Mean Well 12V for that, and a 5v MeanWell for the USB? I admit that I am a newbie in this, so please tell me why this will not work as well with the 1021 as with the 1521